What psoriasis is like: Psoriasis is made of red, scaly plaques that can be itchy and painful. It can show up anywhere but is most commonly found on the scalp, as well as the outside of the elbows and knees. It usually starts between age 10 and 30 and tends to be a chronic condition. “It’s a stubborn disease that waxes and wanes, so people have it for their whole lives,” says dermatologist Paul Cohen.
What causes psoriasis: This skin rash is the result of your immune system attacking the skin’s cells, and creating new ones too quickly, which then build up into the plaques. There’s no one single cause, but the condition runs in families. Stress, obesity, smoking and having many infections (particularly strep throat) increase your risk.
How to treat psoriasis: The first step is generally topical steroids, which can be used for a week or two at a time to clear up the plaques. For ongoing treatment, people use a synthetic form of vitamin D (which slows skin growth), medicated shampoos and retinoids (a topical version of vitamin A). Daily exposure to sunlight also seems to help, as does moisturising well. For more serious cases, options include oral medications that suppress the immune system and phototherapy done in a doctor’s office with a special light. (Discover more applications of light therapy.)
Possible red flag: Serious cases can involve the joints, a condition called psoriatic arthritis. Also, psoriasis increases your chances of having some other diseases, including type 2 diabetes, cardiovascular disease and autoimmune conditions such as Crohn’s – all of which are, like psoriasis, linked to inflammation.
What hives are like: Hives are itchy, raised welts that often have a red ring around them. Their most salient characteristic is that they disappear after about a day, only to show up later in a different location. They come in two forms: acute, which lasts six weeks or less, and chronic.
What causes hives: Hives are often the result of the body releasing histamine as part of an allergic reaction to drugs, food or some other irritant. They also commonly appear after a viral illness, as a side effect of your immune system revving up to battle the disease. “There are a number of potential triggers,” says dermatologist Katie Beleznay. In most cases, she adds, the specific origin is never determined.
How to treat hives: Since hives are a histamine reaction, over-the-counter antihistamines are the first line of defence. If that doesn’t clear them up, ask a doctor if you should use a stronger antihistamine or oral prednisone, an anti-inflammatory medication.
Possible red flag: Rarely, people suffer from ongoing outbreaks of hives almost daily for six weeks or more, a condition called chronic idiopathic urticaria (CIU). The treatment for CIU is the same as for regular hives, but in some cases, it can also be a sign of an underlying thyroid disease or cancer.
What eczema is like: Eczema presents as patches of red, scaly skin that are extremely itchy, especially at night. These rashes often appear on the inside of your elbows and knees. If it’s more serious, the skin might blister or look thickened and white in those areas.
What causes eczema: Eczema is the result of having a weakened skin barrier, which can lead to inflammation and an overreaction from your immune system. Most people are born with it, and your genes are partly to blame. “You’re more predisposed to eczema if you have a family history of asthma, hay fever or the condition itself,” says Lisa Kellett, a dermatologist in Toronto. Some research also suggests that it might be a reaction to pollution, or to not being exposed to enough germs in childhood. (Kids who have dogs, for example, are less likely to have eczema.)
How to treat eczema: For general maintenance, apply a thick, hypoallergenic moisturizer to affected areas immediately after a bath or shower and at night. More serious flares will need topical prescription steroid creams or non-steroid immunosuppressant creams. People with stubborn eczema might also try phototherapy, which uses UVB light to help calm your immune system and reduce itchiness.
Possible red flag: Rarely, what looks like eczema is actually skin cancer, as both can appear red and scaly. “The difference with skin cancer is that it doesn’t go away if you use a steroid,” says Kellett.